The fracture that occurs most frequently without respect to age is the femoral fracture. Reportedly, 150,000 persons suffer from femoral fracture every year in Japan. This is a serious social problem because aged persons tend to need nursing care once they suffer from femoral fracture.
Known methods for curing femoral fracture include replacement of the bone head with an artificial bone head, bonding the fractured parts with an implant, and conservative treatment. The second method (osteosynthesis) is preferred because it employs the patient's own tissue and is minimally invasive. Osteosynthesis in this case is accomplished by internally fixing the femur.
The implant (such as nail, screw, and pin) used for osteosynthesis of the femur is usually designed such that it is arranged in the lengthwise direction of the neck of the femur to stabilize the fractured part. An example of the implant for femoral osteosynthesis is a lag screw screwed into the bone head across the fracture plane in the neck of the femur, as disclosed in Japanese Patent Laid-Open Nos. Hei 11-137566 and 2009-207710.
When the screw type implant is used to fix the fractured part, it is common practice to previously insert a Kirschner wire into the neck of the femur in order to prevent the fractured part from being turned by the torque around the axis along the lengthwise direction of the neck of the femur which is produced as the lag screw is screwed in. The Kirschner wire (called “K wire” for short hereinafter) is arranged to penetrate the cartilage which is called epiphysis line, existing in the bone head. The K wire helps the screw type implant advance to the desired position, and it is then withdrawn after the implant has been screwed into the bone.
Osteosynthesis for femoral fracture with an implant has the possibility of causing ischemic disorder such as bone head necrosis and LSC (Late Segmental Collapse) if the fracture involves the breakage of blood vessels (especially the inside and outside femoral circumflex arteries) which supply blood to the bone head. Unfortunately, there is not any established procedure for preventing and curing such ischemic disorder despite a strong desire.